eth: continue after whitelist check

[holiman]

The whitelist mechanism got broken in #23576, afaict, making it so that if the whitelist check succeeds, the code stalls. The peer is left somehow neither accepted nor rejected, in a state where it's marked as shutting down but not actually kicked out.

This is the cause behind #24202 .
Also, aside from not being able to sync, it also (on my test) causes failure to shut down.

With this fix, I was able to start syncing with peers after the check completes.

[holiman]

Also, aside from not being able to sync, it also (on my test) causes failure to shut down.

Without the PR, on shutdown, a lot of peers are stuck on wg.Wait here:

sync.runtime_Semacquire(0xc0055fc150)
	runtime/sema.go:56 +0x45
sync.(*WaitGroup).Wait(0xc0055fc148)
	sync/waitgroup.go:130 +0x65
github.com/ethereum/go-ethereum/p2p.(*Peer).run(0xc0055fc120, 0x1428e40, 0xc004a4bd80, 0x0)
	github.com/ethereum/go-ethereum/p2p/peer.go:291 +0x333
github.com/ethereum/go-ethereum/p2p.(*Server).runPeer(0xc000143b80, 0xc0055

This is due (I think) to the peer threads being stuck waiting for the res to return here:

goroutine 638 [chan receive, 29 minutes]:
github.com/ethereum/go-ethereum/eth/protocols/eth.(*Peer).dispatchResponse(0xc0050b1ba0, 0xc005874180, 0xc005b47700, 0x0, 0x0)
	github.com/ethereum/go-ethereum/eth/protocols/eth/dispatcher.go:174 +0x32c
github.com/ethereum/go-ethereum/eth/protocols/eth.handleBlockHeaders66(0x1969610, 0xc00134e5a0, 0x19560f8, 0xc005874120, 0xc0050b1ba0, 0xc06e2bdeb22d8111, 0x6d264dab5)
	github.com/ethereum/go-ethereum/eth/protocols/eth/handlers.go:367 +0x1d9
github.com/ethereum/go-ethereum/eth/protocols/eth.handleMessage(0x1969610, 0xc00134e5a0, 0xc0050b1ba0, 0x0, 0x0)
	github.com/ethereum/go-ethereum/eth/protocols/eth/handler.go:215 +0x46f
github.com/ethereum/go-ethereum/eth/protocols/eth.Handle(0x1969610, 0xc00134e5a0, 0xc0050b1ba0, 0xc002c1a600, 0xc0000c09a0)
	github.com/ethereum/go-ethereum/eth/protocols/eth/handler.go:154 +0x45
github.com/ethereum/go-ethereum/eth/protocols/eth.MakeProtocols.func1.1(0xc0050b1ba0, 0x17ce820, 0xc004657440)
	github.com/ethereum/go-ethereum/eth/protocols/eth/handler.go:111 +0x3d
github.com/ethereum/go-ethereum/eth.(*handler).runEthPeer(0xc00134e5a0, 0xc0050b1ba0, 0xc0055cf710, 0x0, 0x0)
	github.com/ethereum/go-ethereum/eth/handler.go:444 +0xc05
github.com/ethereum/go-ethereum/eth.(*ethHandler).RunPeer(0xc00134e5a0, 0xc0050b1ba0, 0xc0055cf710, 0xc0050dc6e0, 0x7f5481ee4d78)
	github.com/ethereum/go-ethereum/eth/handler_eth.go:41 +0x3f
github.com/ethereum/go-ethereum/eth/protocols/eth.MakeProtocols.func1(0xc0055fc120, 0x1954b40, 0xc0050dc6e0, 0x0, 0x0)

[karalabe]

Good catch.

@holiman Are the hangs before or after this PR?

[holiman]

The hangs are without this PR (edited to clarify)

[karalabe]

LGTM

[mohamedmansour]

For inclusivity should we rename it to allowlist?

[ryanschneider]

For inclusivity should we rename it to allowlist?

I definitely agree a more inclusive (and descriptive!) name would be better, I'll start a PR that deprecates the current name and chooses a new one as soon as I can, will link it here when ready.